How To Test For A Blown Head Gasket (GM 3.5L -FWD)

There are four easy tests to check for a blown head gasket, and in this tutorial, I'm gonna' show you how to perform them in a step-by-step fashion.

Two of the four tests can be done in minutes and with absolutely no tools. The other two are done with a compression tester and a block tester. With you test results, you'll quickly get to the bottom of the issue on 3.5L front wheel drive (FWD) GM vehicle.

Symptoms Of A Blown Head Gasket

The most common cause of a blown head gasket is that the engine overheated due to one of the following:

• The radiator fan is not working.
• The engine ran without coolant (due to a leak somewhere in the coolant system).
• The thermostat went bad and is stuck closed.

The most common symptoms a blown head gasket are:

• Your car or mini-van is overheating. You know it's not the fan or thermostat.
• White smoke is coming out of the tail-pipe and it smells like anti-freeze being cooked.
• The car or mini-van won't start.
  • You have already verified it's not an ignition system problem because you have spark coming out at all of the spark plug wires.
  • You know it's not a lack of fuel, because you have verified that the fuel pump is delivering fuel to the fuel injectors.
• The engine oil is thick and tan to off-white color.

TEST 1: Engine Oil The Color Of ‘Coffee With Too Much Creamer’

The very first thing, not too mention that it's the easiest, is to check to see if coolant has mixed with the engine oil.

This simply involves removing the engine oil dipstick and checking the color of the oil. If this test doesn't prove you've got a blown head gasket, then the next step is test 2 in the next page.

OK, I'll stop talking and we'll get this show on the road, this is what you need to do:

1. 1

   Open your vehicle's hood.

2. 2

   Pull the engine oil dipstick out of the engine.

3. 3

   Visually check the color of the oil and its viscosity (that's on the dipstick).

4. 4

   You'll see one of two things:
   
   1.) The oil on the dipstick is a creamy tan and is thick.
   
   2.) The oil on the dipstick is its normal color and viscosity.

Take a look at the following interpretations to find out which one best fits what you have observed of the color of the oil:

CASE 1: The color of the oil is a light tan, like coffee with too much creamer. This confirms that the head gasket is blown and that it's letting coolant mix with the engine oil.

If you're wondering why the oil looks like this? The principal reason is that your FWD 3.5L equipped GM vehicle over-heated and:

1.) The cylinder head warped which caused the head gasket to burn.

2.) And a burned head gasket can not seal the oil and coolant ports in both the engine block and the cylinder head (especially with a warped cylinder head).

3.) This leads to the coolant entering the engine oil pan. As both oil and coolant mix, the resulting combination gets thick and becomes an off-white color.

CASE 2: The color of the engine oil is normal. Although this is a good result, it does not confirm the condition of the head gasket yet, go to: TEST 2: Combustion Gases Expelled From An Open Radiator.

Here's why: In the majority of the cases, a blown head gasket will cause the engine's coolant to mix with the oil, but not always. Therefore one or maybe two more tests are needed to make sure that the head gasket is really blown or not. The next test is to see if the engine's compression/combustion gases are escaping thru' the radiator.